This invention relates to water-swellable, absorbent aerated films or laminates made from lightly cross-linked polyelectrolytes and their application in the field of soil modification to enhance the water capacity and air capacity of the soil matrix.
The patent application by W. D. Burkholder, Ser. No. 565,880, filed Apr. 7, 1975 (now abandoned), discloses methods of curing polyelectrolytes to make water-swellable films wherein the curing or cross-linking agent is a polyamido-polyamine epichlorohydrin adduct. The patent to J. R. Gross, U.S. Pat. No. 3,980,663 discloses absorbent articles, films, etc. and methods for their preparation wherein the cross-linking agents are reactive with carboxylate groups. The patent to Robert E. Erickson, U.S. Pat. No. 4,117,184, discloses that when films and laminates are mechanically aerated prior to the curing step, one can prepare a water-swellable, aerated film or laminate which exhibits enhanced fluid absorbency and flexibility.
It is well-known that absorbent polymers added to soil matrixes will increase the water-holding capacity of the soil. The prior-known methods added finely divided particulate absorbent powder to the soil matrix. Several problems became evident when the soil matrix was modified by particulate absorbent. The absorbent particles tend to shift position in the dry soil during mixing or working the soil. Also, only very low concentrations of absorbent polymer can be used without causing a sealing effect in the soil. Thus, water or air cannot percolate through the soil when this sealing effect occurs. The absorbent film/tissue laminate solves many of these problems since it can be placed into the soil where it is needed without sealing the soil and also due to its physical form does not shift in the soil.